Electronic Switching: Help!

[Macaba]

If I had 20 sources of voltage on one piece of hardware, and 20 inputs on another, how could I electronically switch this to give any combination of sources to inputs. (Thats approx 400 combinations)

Any solutions can use a PIC Microcontroller, as its my intention to use this to interface with a computer and control the switching. This has 34 channels of input/output. With output voltage being 5V.

Perhaps I can use 9 outputs in binary form to give 512 values. But how would this translate to the switching?
Perhaps there is an IC that does this already and can interface over SPI to the microcontroller?

I'd ideally have a solution with as low a part count I can get.

Thanks

Mac

[jksuperstar]

Just to make sure I understand you: there are 20 analog signals, or 20 digital 5v (on-off) signals?

For analog, your options are a little limited for very small part-counts, since you'll need basically 20x (20 input mux or mixers). Where as for digital signals, you could use a CPLD or the PIC itself to do the multiplexing.

For analog, you could do one of the following (all use a PIC as control)
1.) Limit yourself to 16 ins & outs, since you could use the analog devices ADG506A, and just put 16 of them down.

2.) The ADG731 supports 32 inputs, but for $5 ea, you'd need 20 of them.

3.)Or you can go with one of these:
http://www.analog.com/en/prod/0,,768_832_AD8113%2C00.html
(though on the site they are $30us each - still cheaper than 20 x some other part though! Unfortunatly, it's a surface mount LQFP package, not thru-hole DIPs).

4.) Use many of the analog switches, such as these:
http://www.analog.com/en/subCat/0,2879,768%255F833%255F0%255F%255F0%255F,00.html
And switch channels on, and dump them into a 20->1 mixer (resistor-opamp mixer). Then you could either use it as a matrix, or a mixer. These parts a cheap & easy to work with though.

[Macaba]

20 analog signals.

My idea goes like this- simple computer controlled analog synthesizer. I see there are already things like this on the market, but i'm stunned at the prohibitive price.

I'm tempted to just make an 'add-on' module for the soundlab, in which case would require far less switches. As a proof of concept.

As for voltage control- DAC, I would use a single digital potentiometer, and switch this across all the voltage inputs at the correct stored voltage. Each voltage input has a S&H on it, so it would retain the voltage for a certain time. Its rather like RAM, you refresh it every so often, sometimes with same values or changing values. This is my idea to keep the part count down for this particular thing.

I'm tempted to say that you could make a digital interface soundlab. It has an graphical LCD display, and about 4 rotary encoders. So you could switch to each module and increment the virtual pots with the correct encoder. But i'm getting ahead of myself.
I may just do it....

I could just about use normal SOIC style components, but no smaller.

Now to look at musicfromouterspace and see how many lines of switching i'd need for the soundlab!

[jksuperstar]

There are multiple channel digi-pots, (like 6 or so in a package). Just putting 1 where each is needed might be a lower part count than you think (20/6 = 4, with 4 extra!). Also, there are 8/10/16 channel dacs that you could use for even less parts (good for digital envelope generators, digital oscillators, etc).

I thought of doing the same thing for my PAIA Fatman, never did it, but I could with a combo of DACs and Digital-Pots. Came down to something like 3 parts (1 DAC + 2 DPots), with 2 serial interfaces, one of them chained.

oh - make sure you see how fast those digital pots can be updated, most are limited to several milliseconds slew rate, so updating 20 signals from 1 pot can get audibly slow.

[ian-s]

This has been one of those 'back of my mind' ideas for a long time. Digital version of a EMS synthi pin matrix. Replace the mechanical connections with a vca -> summing mixer array. Reproduce the physical matrix with LED/touch switches. Like you say, instead of just on/off, each intersection stores a 16 bit value. Quad VCA chips are not too expensive and the whole thing would look so cool.
I recently thought that the LED/Switch matrix and micro could double duty as nice 'Tenori-On' style sequential controller.

[v-un-v]

[Macaba]

[ian-s]

[jksuperstar]

Hmmm,

$30 for a 16x16 matrix from analog devices
$5 for a Surf Board to mount the LQFP on
$20 for 16x16 LED dot matrix (could be individual LEDs, or 4 8x8 matrix packages).

I think it could all be done for less than $100, including a processor, post amplification if needed, and the matrix control. Through in some rotary encoders for fun.

So, maybe not very far fetched.

[v-un-v]

[toppobrillo]

heya

replacing patchcords with buttons and menus....hmm. hey wait, isn't that one thing that has sucked about newer synthesizers? maybe they just haven't laid it out properly.

if the ESQ-1 had a knob and a switch for every function it contained, it would be as popular [and as or even more expensive] as your prophet-5s are anyday. it really has alot to do with the physical interface of the machine, i think.

i had an ESQ-1 for a while, and it is a very capable machine, i just couldn't stand cycling thru pages of menus and adjusting the parameters one at a time with a singular slider control. ick. it gets really old.

the ems matrix type of interface for cv routing is a good one, i think.. you could replace those pins with little buttons, sure. it wouldn't be too hard. you could do an 8x8 switching matrix with 4 4051's and 8 S&Hs. each button has a unique 6-bit identity.

or..if you wanna go crazy, you could do a 16x16 [that sure is alot of sources and destinations!] with 4 4067s and 16 S&Hs, where each has an 8-bit id.

a simple computer interface for voltage control is the OMDAC.

also, if you want to use a single control for many functions check out the moog source.

maybe these will at least give you some ideas.